This document describes a proposal to study the epidemiology of intracranial meningiomas in adults and of primary brain tumors of all histologic types in children to test the hypothesis that previous radiation exposure is causally related to the development of these tumors, to test previously suggested causal associations, to discover new associations and to delineate the characteristics of the high risk groups. The study proposed is a large case control study to be performed in Los Angeles County. It has been designed to permit simultaneous examination of multiple antecedent risk factors. Cases with specified intracranial tumors will be identified by the LAC/USC Cancer Surveillance Program. Questionnaires have been designed to obtain data on radiation exposure, occupation, consumption of tobacco and drugs, medical history, and family history of tumors. Standard matched pair analyses of multiple variables will be performed on the data from the questionnaire.